The use of molecular sieves as catalytic agents in hydrocarbon conversion processes is relatively well known. It has previously been suggested that, unlike in cracking-based (e.g., FCC) or dehydration-based (e.g. ETE) hydrocarbon conversion processes, molecular sieve catalysts in carbon-assembling processes (e.g., OTO/MTO) can benefit from organic material within the pore structure of the molecular sieve that can act as co-catalysts.
Coincidentally, there have been studies of oxygenates-to-olefins reaction systems (carbon-assembling processes) that indicate transformation of the oxygenate feedstock into organic material within the molecular sieve pore structure in an initial induction period. It has been suggested that the organic material formed within the molecular sieve during this initial induction period further catalytically enhances oxygenate conversion, e.g. into olefins, in OTO processes.
As a result, some publications have advocated pre-pooling, or pre-treating a molecular sieve catalyst with feedstock that reacts to form organic material similar to (if not identical to) the organic material formed during the initial induction period, in order to take advantage of the supposed further catalytic effect of such organic material within the already catalytic molecular sieve. Exemplary disclosures suggesting such molecular sieve pre-treatments include, but may not be limited to, U.S. Pat. Nos. 6,441,262, 6,444,868, 6,482,999, 6,518,475, 6,657,022, 6,734,330, 6,734,747, 6,844,476, 7,045,672, 7,057,083, 7,084,319, 7,132,581, and 7,199,277, as well as U.S. Patent Application Publication No. 2006/0135834 A1.
Nevertheless, such pre-treatments, by their reactive nature, tend to yield a wide distribution of organic materials within the molecular sieve pore structure. Indeed, due to the breadth of variety of the organic material formed during a pre-treatment, some portion of these organic materials may be non-catalytic or detrimental to the catalytic influence of the molecular sieve in the oxygenate conversion reactions they were intended to enhance.
Furthermore, particularly when relatively small pore molecular sieves (i.e., pore size of about 5 Å or less) are utilized as primary catalysts for MTO/OTO conversion reactions, the relatively small pore openings tend to limit the types of organic material precursors that can be used in the pre-treatment process.